import {
  IsString,
  IsEmail,
  IsNumber,
  IsOptional,
  MinLength,
  MaxLength,
  Min,
  Max,
  IsArray,
  IsBoolean,
  IsEnum,
  Matches,
} from "@dangao/bun-server";

class CreateUserDto {
  @IsString()
  @MinLength(2)
  @MaxLength(50)
  name: string;

  @IsEmail()
  email: string;

  @IsNumber()
  @Min(0)
  @Max(150)
  @IsOptional()
  age?: number;

  @IsString()
  @MinLength(8)
  @Matches(/^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)/)
  password: string;
}

Use in Controller

import { Controller, POST, Body, Validate } from "@dangao/bun-server";

@Controller("/api/users")
class UserController {
  @POST("/")
  @Validate(CreateUserDto)
  createUser(@Body() data: CreateUserDto) {
    return this.userService.create(data);
  }
}

Common Validation Decorators

Type Validation

@IsString()      // Must be string
@IsNumber()      // Must be number
@IsBoolean()     // Must be boolean
@IsArray()       // Must be array
@IsObject()      // Must be object
@IsDate()        // Must be date

String Validation

@IsEmail()                       // Email format
@IsUrl()                         // URL format
@IsUUID()                        // UUID format
@MinLength(5)                    // Minimum length
@MaxLength(100)                  // Maximum length
@Matches(/^[a-z]+$/)             // Regex match
@IsNotEmpty()                    // Non-empty string
@IsAlpha()                       // Letters only
@IsAlphanumeric()                // Letters and numbers

Number Validation

@Min(0)          // Minimum value
@Max(100)        // Maximum value
@IsPositive()    // Positive number
@IsNegative()    // Negative number
@IsInt()         // Integer

Array Validation

@IsArray()
@ArrayMinSize(1)
@ArrayMaxSize(10)
@ArrayUnique()
items: string[];

Enum Validation

enum UserRole {
  ADMIN = "admin",
  USER = "user",
}

class UpdateRoleDto {
  @IsEnum(UserRole)
  role: UserRole;
}

Optional and Conditional

@IsOptional()           // Optional field
@IsNotEmpty()           // Cannot be empty
@ValidateIf(o => o.type === "email")  // Conditional validation

Nested Object Validation

import { ValidateNested, Type } from "@dangao/bun-server";

class AddressDto {
  @IsString()
  street: string;

  @IsString()
  city: string;
}

class CreateUserDto {
  @IsString()
  name: string;

  @ValidateNested()
  @Type(() => AddressDto)
  address: AddressDto;
}

Array Element Validation

class CreateOrderDto {
  @IsArray()
  @ValidateNested({ each: true })
  @Type(() => OrderItemDto)
  items: OrderItemDto[];
}

Custom Validators

import { registerDecorator, ValidationArguments } from "@dangao/bun-server";

function IsStrongPassword() {
  return function (object: any, propertyName: string) {
    registerDecorator({
      name: "isStrongPassword",
      target: object.constructor,
      propertyName: propertyName,
      validator: {
        validate(value: any) {
          if (typeof value !== "string") return false;
          return (
            value.length >= 8 &&
            /[a-z]/.test(value) &&
            /[A-Z]/.test(value) &&
            /\d/.test(value)
          );
        },
        defaultMessage() {
          return "Password must be at least 8 characters with uppercase, lowercase and number";
        },
      },
    });
  };
}

// Usage
class RegisterDto {
  @IsStrongPassword()
  password: string;
}

Custom Error Messages

class CreateUserDto {
  @IsString({ message: "Name must be a string" })
  @MinLength(2, { message: "Name must be at least 2 characters" })
  name: string;

  @IsEmail({}, { message: "Please enter a valid email address" })
  email: string;
}

Validation Error Handling

Validation failures throw ValidationError:

import { ValidationError, HttpException } from "@dangao/bun-server";

// Global error handler
function errorHandler(ctx: Context, next: NextFunction) {
  try {
    return next();
  } catch (error) {
    if (error instanceof ValidationError) {
      return new Response(JSON.stringify({
        statusCode: 400,
        message: "Validation failed",
        errors: error.errors,
      }), { status: 400 });
    }
    throw error;
  }
}

Partial Validation (Update Scenarios)

import { PartialType } from "@dangao/bun-server";

// Inherit from CreateUserDto, all fields become optional
class UpdateUserDto extends PartialType(CreateUserDto) {}

// Or define manually
class UpdateUserDto {
  @IsOptional()
  @IsString()
  @MinLength(2)
  name?: string;

  @IsOptional()
  @IsEmail()
  email?: string;
}

Query Parameter Validation

class PaginationDto {
  @IsOptional()
  @IsNumber()
  @Min(1)
  page?: number = 1;

  @IsOptional()
  @IsNumber()
  @Min(1)
  @Max(100)
  limit?: number = 10;
}

@Controller("/api/users")
class UserController {
  @GET("/")
  @Validate(PaginationDto, "query")
  list(@Query() query: PaginationDto) {
    return this.userService.paginate(query.page, query.limit);
  }
}

Use in Controller

Common Validation Decorators

Type Validation

String Validation

Number Validation

Array Validation

Enum Validation

Optional and Conditional

Nested Object Validation

Array Element Validation

Custom Validators

Custom Error Messages

Validation Error Handling

Partial Validation (Update Scenarios)

Query Parameter Validation

Related Resources

bun-server-validation

Bun Server Data Validation

Basic Usage

Define DTO with Validation Rules